Methemoglobinemia: A Case Report

Abstract

Methemoglobinemia ansmg from the use of local anesthesics, such as benzocaine, prilo­ caine and lidocaine, is a potential complica­ tion in the dental operatory. Its recognition is critical, because failure to treat the condition can result in death . Occurrences during intu­ bation have been reported in the medical liter­ ature, but methemoglobinemia has not been widely discussed in dentistry. CASE REPORT A forty-seven year old, white, male physi­ cian presented to the dental clinic at the University of Maryland Medical Systems. He stated, "The use of local anesthetics causes my blood to turn chocolate brown, it is in my medical record." His medical history included hepatitis, hypertension, and difficulty of intu­ bation (secondary to anatomy). He was taking Prozac for an obsessive-compulsive disorder. On December 28, 1990 he was admitted to the hospital for elective surgical removal of his third molars. Prior to intubation vital signs were: blood pressure-I 7011 12 mm/Hg, pulse-II O/minute, respiration-24/minute. Hemoglobin tested 14 g/dL. Oxygen saturation and pulse oxymetry levels were 99%. The lungs were clear and there was a normal flow murmur over the left sternal border. The abdomen was unremark­ able and the extremities were cyanotic with and pulses were present. Before and during intubation the following medications were used: midazolam HCl, glyco­ pyrrolate, Droperidol, Fentanyl, lidocaine, ceta­ caine, surital and Neosynephrine. During intu­ bation the patient became cyanotic. His O 2 satu­ ration dropped to 74%. During and after attempted incubation chest radiographs were normal. During surgery laboratory data was as fol­ lows: hemoglobin-I 1.7 g/ dL wi th oxyhemo­ globin-64.5%, carboxyhemoglobin 1.7% and methemoglobin-33.2%. The blood gases were pH -7.59, pCO r 24, pOr584, on a FI0 2 of 100%. The immediate assessment was that the cya­ nosis was secondary to methemoglobin reduc­ tase deficiency or toxic methemoglobinemia.